The disclosed invention is directed generally to an optical drop detect, and more particularly to an optical drop detect that is capable of detecting relatively small drops of two different sizes.
Optical drop detect circuits are utilized in ink jet printers for various purposes including testing of the operation of ink drop firing nozzles of a printhead and determination of the relative positions of the nozzle arrays of multiple printheads. Optical drop detect circuits typically include a light sensor such as a photodiode which senses the light provided by a light source such as an LED. When a drop is present in the light path between the light sensor and the light source, the output of the light sensor changes since the amount of light sensed by the light sensor is reduced by the presence of the ink drop. The output of the light sensor is typically amplified and analyzed to determine whether an ink drop passed through the light path between the light source and the light sensor.
Considerations with known optical drop detect circuits include their inability to reliably detect relatively small sizes of ink drops, and the inability to reliably detect a plurality of different sizes of relatively small ink drops.